Its pretty common for people to have Bipolar and Borderline.

Bipolar is "typically " treated with meds, CBT and coping skills

Borderline , Meds might help some ,, but DBT therapy is more helpful.

I dont really understand why your Pdoc would say that BP meds would instigate depression and anxiety

She said she can tell your moods are leveling out but dropped your dosages? Lithium only works if you in a theraputic levels , so dropping it down might take you out of the "window" in which lithium would help you or not. Lamictal typically only helps on the depressive end of Bipolar . so dropping that also doesn't really make sense to me

Call your local mental health services for your city or county and see if you Qualify for sliding scale or even free Therapy or group for BP and BPD

Hope you feel better soon